1. Field of the Invention
The present invention relates to a process for preparing carbocyclic or heterocyclic nitriles. Particularly, the present invention relates to a process for preparing carbocyclic or heterocyclic nitriles comprising subjecting a carbocyclic or heterocyclic compound to ammoxidation via vapor phase catalytic fluidized bed reaction. The carbocyclic or heterocyclic nitrites are useful as intermediates for a variety of pharmaceutical or agricultural chemicals, functional chemicals, polymers, and the like.
2. Background Art
As the process for preparing these nitrites are known a variety of methods, among which a method comprising the ammoxidation of carbocyclic or heterocyclic compounds has also been proposed as one of the important methods.
A variety of methods have been proposed for preparing carbocyclic nitrites via the vapor phase ammoxidation. Thus, Japanese Patent Laid-Open Publication No. 13141/1974 (U.S. Pat. No. 3,803,204) discloses a method comprising ammoxidation of xylene or toluene in the presence of a Mo catalyst, and Japanese Patent Laid-Open Publication No. 90238/1978 (U.S. Pat. No. 4,124,631) discloses a method comprising ammoxidation of methyl-substituted aromatic compounds in the presence of a V-P catalyst. Also, Japanese Patent Laid-Open Publication Nos. 13944/1981 (U.S. Pat. No. 4,336,205) and 120351/1987 (U.S. Pat. No. 4,814,479) disclose an ammoxidation method of alkyl aromatic compounds in the presence of a V-Sb catalyst; Japanese Patent Laid-Open Publication No. 10753/1988 discloses an ammoxidation method in the presence of a Sbxe2x80x94Sn catalyst; Japanese Patent Laid-Open Publication No. 63563/1989 (U.S. Pat. No. 4,939,260) in the presence of a Ti- and Si and/or Zr-containing catalyst; and Japanese Patent Laid-Open Publication No. 170724/1993 (EP 525367) in the presence of a Pxe2x80x94Mo/Si catalyst, respectively. Furthermore, Japanese Patent Laid-Open Publication No. 190646/1988 discloses an ammoxidation method of alkyl aromatic compounds or alkyl-substituted alicyclic compounds in the presence of a Fexe2x80x94Sb catalyst.
A variety of methods have been proposed also for preparing heterocyclic nitrites via the vapor phase ammoxidation. Thus, Japanese Patent Publication Nos. 7511/1965, 13572/1970 and 34673/1974, Japanese Patent Laid-Open Publication No. 4556/1972 (U.S. Pat. No. 3,927,007), Japanese Patent Laid-Open Publication No. 41871/1975 (U.S. Pat. No. 4,001,255), Japanese Patent Laid-Open Publication No. 80864/1976 (U.S. Pat. No. 3,959,297), Japanese Patent Laid-Open Publication No. 17360/1980, Japanese Patent Laid-Open Publication No. 139444/1981 (U.S. Pat. No. 4,336,205), Japanese Patent Laid-Open Publication No. 156038/1982 (U.S. Pat. No. 4,447,612), Japanese Patent Laid-Open Publication No. 208575/1988, and Japanese Patent Laid-Open Publication No. 275564/1989 (U.S. Pat. No. 4,963,687) disclose methods of preparing cyanopyridines from alkyl-substituted pyridines; Japanese Patent Laid-Open Publication Nos. 30382/1974 and 145672/1980, Japanese Patent Laid-Open Publication No. 156039/1982 (U.S. Pat. No. 4,419,272, U.S. Pat. No. 4,496,729), and Japanese Patent Laid-Open Publication No. 81448/1996 (EP 698603) disclose methods of preparing cyanopyrazines from methylpyrazines; Japanese Patent Laid-Open Publication No. 111566/1977 (U.S. Pat. No. 4,055,514) discloses a method of preparing cyanothiazole from methylthiazole; Japanese Patent Laid-Open Publication No. 99360/1987 (U.S. Pat. No. 4,603,207) discloses a method of preparing cyanopyridine from methylpyridine and methylpiperidine; Japanese Patent Laid-Open Publication No. 10753/1988, Japanese Patent Laid-Open Publication No. 72675/1988 (U.S. Pat. No. 4,778,890), Japanese Patent Laid-Open Publication No. 152360/1989 (U.S. Pat. No. 4,778,890), Japanese Patent Laid-Open Publication No. 31730/1989 (U.S. Pat. No. 4,931,561), Japanese Patent Laid-Open Publication No. 31731/1989 (U.S. Pat. No. 4,931,561), Japanese Patent Laid-Open Publication No. 31769/1989 (U.S. Pat. No. 4,931,561), Japanese Patent Laid-Open Publication No. 63563/1989 (U.S. Pat. No. 4,939,260), Japanese Patent Laid-Open Publication No. 126548/1992 (U.S. Pat. No. 5,139,988), and Japanese Patent Laid-Open Publication No. 170724/1993 (EP 525367) disclose methods of ammoxidation of alkyl-substituted heterocyclic compounds to prepare nitriles; and Japanese Patent Laid-Open Publication No. 190646/1988 discloses a method of ammoxidation of alkyl-substituted heterocyclic compounds or alkyl-substituted alicyclic compounds, respectively, to prepare corresponding nitrites.
While giving high yields of carbocyclic or heterocyclic nitriles, these methods had many problems to be solved in the case of the commercial production, particularly in the case of the large scale production of these nitriles. That is, the synthetic reaction of nitrites by the vapor phase catalytic ammoxidation of carbocyclic compounds or heterocyclic compounds evolved a large amount of reaction heat, and thus there was a problem of local overheating in the large scale production of nitrites which led to the difficulty in controlling the reaction temperature and thus increased the formation of by-products resulting in the lowering of the yield of the nitriles as the desired products. There was also a problem of the lowering of the yield of the nitrites as the desired products with the passage of time due to the deposition of carbonaceous matter on the catalyst and due to the deterioration of the catalyst used through its reduction. Such phenomena become more distinguished as the supply gas has a higher concentration of the carbocyclic compound or heterocyclic compound as the starting material. Therefore, it would have been necessary to lower the concentration of these starting cyclic compounds in the industrial production of carbocyclic or heterocyclic nitriles via the vapor phase ammoxidation reaction. It was also required for eliminating the above described defects in some cases to increase the amounts of ammonia and oxygen used, to add steam in a large amount, or to take into account the introduction of an inert gas in order to remove the composition of the raw material gas from the explosion composition range.
As one of the methods for solving these problems, there may be mentioned the production via fluidized bed reaction. However, this method still had problems to be solved such as the substantial lowering of the yield of the objective product due to the lowering of the catalyst activity with it the passage of time in the ammoxidation reaction is a fluidized bed technology is simply applied as illustrated hereinafter in comparative examples. It is duly noted that it was recommended in Japanese Patent Laid-Open Publication No. 41871/1975 (U.S. Pat. No. 4,001,255), Japanese Patent Laid-Open Publication No. 275564/1989 (U.S. Pat. No. 4,963,687) and Japanese Patent Laid-Open Publication No. 170724/1993 (EP 525367) that the ammoxidation reaction of heterocyclic compounds should be carried out in a fluidized bed. However, there remained problems to be solved such as substantial lowering of the yield of the objective product due to decrease in the catalyst activity with the passage of time even when the ammoxidation reaction is carried out simply over a fluidized bed catalyst as illustrated hereinafter in comparative examples.
The present invention has been made for the purpose of solving the problems in the prior art described above, and the object of the present invention is to provide an economically advantageous process for preparing nitrites comprising subjecting carbocyclic compounds or heterocyclic compounds to ammoxidation via vapor phase catalytic fluidized bed reaction to prepare the corresponding nitriles, in which the reaction is carried out effectively without the necessity of increasing the amount of ammonia or oxygen used or the necessity of introduction of steam in a large amount to give the nitriles as the objective products stably with the passage of time in a high yield with a high selectivity.
The present inventors have now found that a method for supplying starting materials for the reaction can be successfully designed to suppress the accumulation of carbonaceous matters deposited on the catalyst and to suppress the deterioration of the catalyst due to reduction, so that the carbocyclic or heterocyclic nitriles as the objective products are obtained in high yields, thus having reached the present invention.
The present invention accordingly relates to a process for preparing nitrites comprising subjecting a carbocyclic compound or a heterocyclic compound to ammoxidation via vapor phase catalytic reaction in a fluidized bed reactor, in which the reaction is carried out in the presence of a vanadium- and/or molybdenum-containing metal oxide catalyst, oxygen-containing gas being supplied through an oxygen-containing gas inlet provided at the bottom of the fluidized bed reactor, a carbocyclic compound or a heterocyclic compound and ammonia being supplied at a level higher than the oxygen-containing gas inlet, a fluidized bed being formed so that the ratio of the amount of catalyst (Wb) fluidized at a level higher than the inlet of the carbocyclic compound or heterocyclic compound to the amount of catalyst (Wa) fluidized at a level higher than the oxygen-containing gas inlet in the reaction zone is in the range of Wb/Wa of 0.01 to 0.95 by weight.